Math Forum / Mathematics / Algebra Help / April 2008

Take x and y to be integers.
If we have a set P(m) comprising the first m primes beneath a value z, and a
general subset J of of P(m), then I am constructing a matrix M_1 in which
the members of J index the rows.

 I am not trained in maths but have something I want to express, and would
be very grateful for advice as to how to write it in a professional, if not
necessary exclusively mathematicaly formal, manner.
I am trying to define a set R(n) for intervals [x,y] and [x',y'] such that n

The rationals form a ring with addition defined as
                       p/q + r/s = (ps + qr)/qs.
I'm used to the fact that this works for the addition of fractions as we
want to; for example, a basket with half of 10 oranges if dumped on a

In the book, Algebra Demystified," the author presents this problem as
the part of the final book review (problem #57):
4x(x-3) - 5(3x-6) = (2x - 3)2
The author's answer is 7/5, which is correct.

It has been a long time since I made a C in Algebra in high school.  I
guess I should have paid more attention because I have a real life
problem that needs algebra to solve.
my equation:

What would the formula be?
In a bag of  red and black marbles there are 18 fewer red marbles than black
If 45% of the marbles are red how many marbles are in the bag.

Back in school 30-odd years ago I was taught that monthly
interest on a loan/investment is the 12th root of the annual
interest, ie: loan=loan*((1+apr/100)^(1/12)).
Doing a bit of checking for some source code I find

I'm updated some sample code for a tutorial and I've got
working code for various loan calculations.
Dredging through my memory I'm sure I was taught back
at school how to calculate repayments that go down as

Please help me with the correct approach to the solution for (2x-1)(x
+3)<=9 .
We get multiple choice answers, like 1) x <= -4 or x >= 3/2  or 2) -4
<= x <= 3/2

I have a mathematical puzzle that I cant solve.
In the table below, the inputs are the values in columns "A" and "B
and the desired output is column "C".
  A        B       C